This invention relates to the field of mechanical refrigeration units using halogen containing compounds, especially Freon and its derivatives. Freon and its related compounds are known and widely used as heat transfer media in mechanical refrigeration apparatus, including units intended for unattended operation such as truck and trailer mounted units. Such units usually include a refrigerant receiving tank, a pressure vessel for storage of liquid refrigerant, which also may include means for assisting in the condensation of gaseous refrigerant to a liquid state; an evaporator converting the refrigerant into a cold gas, which provides the cooling effect; a condenser for converting the hot gaseous refrigerant into a cooler liquid form, and a compressor which establishes a refrigerant pressure differential around the system, causing refrigerant flow. Since the units include pressurized storage of an evaporative liquid, safety codes require that each system have pressure relief valves, which release refrigerant if internal system pressure rises above a certain level.
More recently, it has become known that release of chlorinated hydrocarbons into the atmosphere is a significant environmental danger. Since typical trailer borne refrigeration systems contain approximately 13 pounds (liquid) of such refrigerants, pressure relief can result in a significant release of such refrigerant.
No system is known to the applicant for capture or prevention of release of refrigerants when an over-pressure situation occurs or a pressure relief valve opens. U.S. Pat. No. 2,682,752 to Branson shows, in the field of petroleum storage, a system in which pressure reacting switches divert vapor from a system to an overflow tank. U.S. Pat. No. 3,736,763 discloses the use of pressure responsive switches to control the flow of fluids in a refrigeration system.